Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
Browse
4 results
Search Results
Article Citation - Scopus: 1Optical and Surface Properties of Zinc Oxide Nanoparticles Dried by Conventional and Supercritical Ethanol Drying Techniques(Research India Publications, 2014) Egbuchunam, Theresa Obuajulu; Yetgin, Senem; Özmıhçı Ömürlü, Filiz; Balköse, DevrimZinc oxide (ZnO) nanoparticles were synthesized by conventional (ZnO-A) and supercritical ethanol drying (ZnO-B). Nitrogen adsorption/desorption analyses were performed to determine the surface areas of the powders. The specific surface area was 28.30m2/g and 10.61 m2/g for ZnO-A and ZnO-B respectively. The powders adsorbed very small amount of CO2with the conventionally dried powder adsorbing more CO2. Supercritical ethanol dried ZnO had ethanol on its surface which was eliminated by vacuum application at room temperature. Both powders had OH groups which were eliminated on heating up to 500°C under vacuum. However, OH groups were present in lower amounts in supercritical ethanol dried ZnO. The powders were characterized by UV-VIS optical absorption and room temperature photoluminescence spectroscopic analyses. The UV-VIS absorption spectrum showed an absorption band at 375nm due to ZnO nanoparticles. The photoluminescence spectrum of ZnO excited at 380nm exhibited three emission peaks: one at 424nm and 490nm corresponding to band gap excitonic emission and another located at 520nm due to the presence of singly ionized oxygen vacancies.Article Citation - WoS: 6Citation - Scopus: 7Preparation and Characterization of Flexible Poly(vinyl Chloride) Foam Films(John Wiley and Sons Inc., 2012) Şahin, Erdem; Yaşar Mahlıçlı, Filiz; Yetgin, Senem; Balköse, DevrimIn this study, the effect of activator ZnO and heating time at 190°C on foaming, gelation, and dehydrochlorination of poly(vinyl chloride) (PVC) plastisol was investigated. For this purpose, a PVC plastisol was prepared by mixing PVC, dioctyl phthalate (DOP), azodicarbonamide (ADC), ZnO, and the heat stabilizers calcium stearate (CaSt 2) and zinc stearate(ZnSt 2). PVC plastisol films were heated for 3, 6, 12, and 24 min periods at 190°C to see the effect of heating time on the gelation and foaming processes of the PVC foam. The time of 12 min was determined to be optimum for the completion of gelation and foaming processes without thermal degradation of PVC. No foaming was observed under the same conditions for the samples without ZnO. ZnO had a significant catalytic effect on ADC decomposition, accelerating the foaming of the films. Average porosity measurement showed a consistent increase in porosity with heating time up to 76% and the average density decreased from 1.17 to 0.29 g/cm 3 on foaming. Tensile tests showed that the tensile strength and tensile strain both increased considerably up to 0.98 MPa and 207%, respectively, with heating time and the elastic modulus was seen to gradually decrease from 4.7 to 0.7 MPa with heating time. Films without ZnO had higher tensile strength since there were no pores. PVC thermomat tests showed that ZnO lowered the stability time of plastigel film with azodicarbonamide.Article Citation - WoS: 17Citation - Scopus: 21Effects of Particle Size and Electrical Resistivity of Filler on Mechanical, Electrical, and Thermal Properties of Linear Low Density Polyethylene-Zinc Oxide Composites(John Wiley and Sons Inc., 2013) Özmıhçı Ömürlü, Filiz; Balköse, DevrimThe effects of particle size and electrical resistivity of zinc oxide (ZnO) on mechanical properties, electrical and thermal conductivities of composites made with linear low density polyethylene (LLDPE) were investigated. Micron sized (mZnO), submicron sized (sZnO), and nano sized (nZnO) powders having resistivities of 1.5 × 106, 1.5 × 109, and 1.7 × 108 were used to prepare composites with 5-20 vol % filler. The tensile strength was lowered and the modulus of elasticity of the composites was increased with ZnO addition. Rather than the particle size of the ZnO, its initial resistivity and aspect ratio affected the resistivity of composites. The resistivity of the LLDPE was lowered from 2.3 × 1016 Ω cm down to 1.4 × 1010 Ω cm with mZnO addition. Thermal conductivity of the composites was increased with ZnO addition 2.5-3 times of the polymer matrix. The composites can be used for electrostatically dissipating and heat sink applications due to their decreased electrical resistivity and increased thermal conductivity.Article Citation - WoS: 10Citation - Scopus: 13Effect of Supercritical Ethanol Drying on the Properties of Zinc Oxide Nanoparticles(Taylor and Francis Ltd., 2012) Egbuchunam, Theresa; Balköse, DevrimThe synthesis, characterization, and application as polymers and anti-wear additives of nanosized zinc oxide particles obtained by conventional and supercritical ethanol drying are reported in this study. The nanaoparticles of ZnO produced by the two different drying techniques were characterized using Fourier Transform Infrared (FT-IR) spectrophotometry, Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and Thermogravimetric analysis (TGA) to elucidate the shape, size, composition, and stability of the nanoparticles. ZnO nanoparticles were then applied to poly (vinyl chloride) (PVC) powder and light mineral oil to assess their effectiveness and suitability as additives in diverse areas. XRD analysis revealed ZnO crystalline structure with average particle size of 24.7 nm for zinc oxide nanoparticles prepared by supercritical ethanol drying while SEM showed well-isolated and monodisperse particles with average size of 61.08 nm. © 2012 Copyright Taylor and Francis Group, LLC.